There are two main objectves to the proposed research. The first is to gain insight into the nature of the growth hormone(GH)-receptor interaction and to study how that interaction leads to the hormone's well characterized effects on protein, amino acid and carbohydrate metabolism. Using structural derivatives of GH that have altered profiles of biological activity, efforts will be made to correlate hormone binding to membrane receptors on isolated target cells with the production of biological effects in those cells. Also, using isolated tissues of hypophysectomized rats, a variety of probes (antibodies against GH, theophylline, microfilament and microtubule modifiers, calcium ionophores) will be employed in an attempt to identify those aspects of cellular function that are involved in transducing the GH-receptor interaction into stimulatory effects on protein synthesis and the membrane transport of amino acids and monosaccharides. The second major objective is to carry out a detailed analysis of the relationship between episodes of enhanced GH secretion and the activity of various metabolic processes influenced by the hormone. The goal is to establish whether or not there is coupling between the episodes of enhanced GH secretion and metabolic activity.